sharepoint - dynamic view of calendar on new item form

I am not certain, what technique to use. Please help me .

We have a sharepoint calendar. This is used to track events. I would need to have a visible indicator , for the user , before he saves the item whether the item is overlaping with other events by project ,开发者_开发百科 by person and time .

This "window" should be changed upon changing the fields begin date and end date.

Do I need to build a complete custom webpart for this ?

What other options do I have?

tx,

Gabliver